The long range goal of this project is to study structure-function relationships in nitric oxide synthase (NOS) and to develop isoform selective NOS inhibitors and drugs. NOS is the enzyme responsible for the biosynthesis of NO, a critically important signaling molecule in the cardiovascular and nervous systems and also is a cytotoxic agents in the immune system. Mammals have 3 NOS isoforms: eNOS (endothelial NOS, regulates blood pressure), nNOS (neuronal NOS, neural signaling), and iNOS (inducible NOS, immune system). The over production of NO by nNOS is associated with a number of neuro-degenerative processes and thus, drugs that selectively block nNOS should be of considerable therapeutic benefit. Selectivity is important since the goal is to block nNOS but not eNOS since eNOS is critical in maintaining proper vascular tone and blood pressure. This is a challenging problem since the active site of all 3 NOS isoforms are nearly identical and a majority of well known NOS inhibitors are not selective. Using a combination of crystallography, computational chemistry, and medicinal chemistry nNOS-selective compounds have been developed, tested, and shown to be very effective in preventing ischemic brain damage in animal models. Our future goals are to further build on this initial work and to exploit new druggable target sites that have been discovered. With respect to structure-function studies, future efforts will focus on conformational dynamics important for function and solving the structure of novel NOSs discovered via bioinformatic searches of new genomes.